During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as monitoring the operability of equipment used during the drilling process or evaluating the production capabilities of formations intersected by the wellbore. For example, after a well or well interval has been drilled, zones of interest are often tested to determine various formation properties such as permeability, fluid type, fluid quality, fluid density, formation temperature, formation pressure, bubble point, formation pressure gradient, mobility, filtrate viscosity, spherical mobility, coupled compressibility porosity, skin damage (which is an indication of how the mud filtrate has changed the permeability near the wellbore), and anisotropy (which is the ratio of the vertical and horizontal permeabilities). These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production.
Tools for evaluating formations and fluids in a well bore may take a variety of forms, and the tools may be deployed down hole in a variety of ways. For examples the evaluation tool may be a formation tester having an extendable sampling device, or probe, and pressure sensors, or the tool may be a fluid identification (ID) tool. The evaluation tool may also include sensors and assemblies for taking nuclear measurements. The evaluation tool may further include assemblies or devices which require hydraulic power. For example, the tool may include an extendable density pad, an extendable coring tool, or an extendable reamer. Other examples of hydraulically powered devices useful in downhole evaluation tools are known to one skilled in the art.
Often times an evaluation tool is coupled to a tubular, such as a drill collar, and connected to a drill string used in drilling the borehole. Thus, evaluation and identification of formations and fluids can be achieved during drilling operations. Such tools are typically called measurement while drilling (MWD) or logging while drilling (LWD) tools. As previously suggested, the tool may include any combination of a formation tester, a fluid ID device, a hydraulically powered device, or any number of other MWD devices as one of skill in the art would understand. As these tools continue to be developed, the functionality, size and complexity of these tools continue to increase. Consequently, multiple tools having different devices and functions may be placed in multiple drill collars. For example, as many as four or more drill collars extending over 40 feet may be needed. The desire to use multiple tools or systems spread over multiple tubular sections in a drilling environment while maintaining the connectability and interchangeability of the tools, as well as the many electrical and fluid connections between the tools, is pushing the limits of current downhole evaluation and identification tools. Further, directly measuring and identifying fluids in such tools becomes increasingly difficult.